Reaction Of Carbonate Research Articles

Isolation of Cationic η3-Allenylnickel(II) Key Intermediate Complexes: Origins of Enantioselectivity and Regioselectivity in Nickel(0)-Catalyzed Asymmetric Propargylic Substitutions.

Herein, we report the synthesis and isolation of cationic η3-allenylnickel(II) complexes that bear rac-BINAP as a bidentate ligand for the first time via Me3SiOTf-promoted C-O bond cleavage of propargylic tert-butyl carbonate. In contrast, in the presence of the monodentate phosphine ligand PEt3, treatment of propargylic tert-butyl carbonate with Ni(cod)2 resulted in a gradual C-O bond cleavage leading to η1-allenylnickel(II) complexes, i.e., trans-(PEt3)2Ni(η1-CPh═C═CHR)(OBoc). X-ray diffraction and NMR spectroscopy studies of [(η3-RCH-CCPh)Ni(rac-BINAP)](OTf) revealed that the complex adopts an η3-allenyl coordination mode both in the crystal lattice and in solution. A thorough structural comparison between [(η3-RCH-CCPh)Ni(rac-BINAP)](OTf) and palladium and platinum analogues revealed that the η3-allenyl moiety in the nickel complex is similar to that observed in palladium and platinum complexes, albeit that each Ni-C bond is shorter than the corresponding Pd-C and Pt-C bonds due to the smaller ionic radius of nickel to that of Pd or Pt. The reactions of either N-methylaniline or sodium N-methylanilide with [(η3-RCH-CCPh)Ni((R)-BINAP)](OTf) furnished (R)-PhC≡CCH(NMePh)Me as an asymmetric propargylic substitution (APS) product with excellent enantioselectivity. Furthermore, when the nickel-catalyzed APS reaction of propargylic tert-butyl carbonate with N-methylaniline was conducted in DMSO at 60 °C in the presence of 5 mol % of [(η3-RCH-CCPh)Ni((R)-BINAP)](OTf) and 7.5 mol % of sodium N-methylanilide as a catalytic precursor and an additive, respectively, (R)-PhC≡CCH(NMePh)Me was obtained in 79% yield with 90% ee. The experimental results and computational calculations strongly suggest that the nickel-catalyzed APS reaction might proceed via a cationic η3-allenylnickel(II) species as the key reaction intermediate.

Precursor influence on the raman spectrum of KNNLiTaLa0.01 prepared by two different methods

This work presents a study of ceramics with the (K0.44Na0.52Li0.04)0.97La0.01Nb0.9Ta0.1O3 composition through their Raman spectra. In the previous studies [1], this particular composition has shown good permittivity and piezoelectric parameter values that justify a deeper investigation. Two sets of samples of these ceramic compounds were prepared using different methods. The first set was prepared using a classical solid-state reaction of oxides and carbonates, as described in Ref. 2. The second set was prepared using the NaNbO3 as a precursor. The Raman spectra of the samples obtained by the direct ceramic method consisted of 4 modes. In contrast, the spectra of the samples obtained using the precursor showed a shift of the wavenumber of the A1g(ν1) mode peak towards lower values and consisted of six modes with the appearance of two additional IR modes, F1u(ν3) and F2g(ν4). Notably, the use of the precursor preparation route led to important improvements resulting in a more straightforward method than that of Saito et al. [3].

Carbon Dots as New Effective Catalysts for Knoevenagel Condensation Reaction and Synthesis of Cyclic Carbonates under Solvent‐free Conditions

AbstractCarbon dots (CDs) as new efficient catalysts have been developed for the Knoevenagel condensation reaction and the synthesis of cyclic carbonates under solvent‐free conditions. Six kinds of carbon dots with different numbers of amino groups were synthesized. The amine‐terminated carbon dot (NCDs‐1) was synthesized using arginine and ethylenediamine by a microwave technique, and its catalytic action was studied. NCDs‐1 with the highest numbers of amino groups was used as new metal‐free and effective heterogeneous catalysts to perform essential Knoevenagel condensation and cycloaddition reactions in solvent‐free conditions. 1H NMR was used to demonstrate the Knoevenagel condensation mechanism, in situ Fourier infrared spectroscopy was used to investigate CO2 cycloaddition and a catalytic mechanism was postulated. NCDs‐1 showed a yield of 96.3±1.5 % for Knoevenagel condensation of benzaldehyde and malononitrile. In addition, NCDs‐1/TBAB showed a yield of (97.0±1.0 %) of 4‐phenyl‐1,3‐dioxolan‐2‐one for styrene oxide at 100 °C and 0.1 MPa in 1.5 h. A simple and convenient method for catalytic reactions with amine‐terminated carbon dots was developed.

An Ab initio based OH initiated oxidation kinetics of glycerol carbonate: A promising biofuel component

The global energy demand is steadily increasing because of the population explosion and economic growth. Fossil fuels supply around 85 % of global primary energy demand. On one hand, fulfilling the increasing energy demands is a big challenge for the next few decades. On the other hand, the continued burning of fossil fuels leads to higher CO2 emissions, severely impacting global warming. Therefore, the policymakers vow to shift from conventional fuels to renewable resources for economic, environmental, and future energy security reasons. In this context, biofuels from lignocellulosic biomass and/or carbon-neutral fuels produced in the sustainable carbon cycle can close the carbon cycle and reach net zero-carbon emission. Recently, glycerol carbonate has been proposed as a promising fuel or fuel additive for future sustainability. Therefore, we investigated the hydrogen abstraction reactions of glycerol carbonate (GC) by OH radicals using high-level ab initio and variational transition state theory calculations. We mapped out the potential energy surface using the CCSD(T)/cc-pV(D, T)Z//MP2/cc-pVTZ level of theory. We used the ab initio parameters to obtain the site-specific rate coefficients by employing the variational transition state theory. We observed that every hydrogen atom in GC displays a unique reactivity with OH radicals. We derived branching ratio of each channel that are difficult to access experimentally. The overall rate coefficients exhibit a strong non-Arrhenius behaviour, which can be represented as:kovCVT/SCT(T)=3.39×10−20×T2.659×e−750.0Jmol−1RTcm3moleculesThis is the first reported rate data for the glycerol carbonate and OH radicals reaction.

Reactions of oximates, aroxides, carboxylates, carbonate, nitrite and tetraarylantimony nitrate with arenesulphone acids

Reactions of oximates, aroxides, carboxylates, carbonate, nitrite and tetraarylantimony nitrate with arenesulphone acids

A review on vegetable oil-based non isocyanate polyurethane: towards a greener and sustainable production route.

The transition from conventional polyurethane (PU) to non isocyanate polyurethane (NIPU) is driven mainly by safety concerns, environmental considerations, and sustainability issues associated with the current PU technology. NIPU has emerged as a promising alternative, addressing limitations related to traditional PU production. There has been increasing interest in bio-based NIPU aligning with the aspiration for green materials and processes. One important biomass resource for the development of bio-based NIPU is vegetable oil, an abundant, renewable, and relatively low cost feedstock. As such, this review aims to provide insight into the progression of NIPU derived from vegetable oils. This article highlights the synthetic and green approach to NIPU production, emphasizing the method involving the polyaddition reaction of cyclic carbonates and amines. The review includes case studies on vegetable oil-based NIPU and perspectives on their properties. Further, discussions on the potential applications and commercial importance of PU and NIPU are included. Finally, we offer perspectives on possible research directions and the future prospects of NIPU, contributing to the ongoing evolution of PU technology.

Palladium-catalyzed enantioselective umpolung allylation of amido-tethered allylic carbonates with isatin-derived ketimines.

A palladium-catalyzed enantioselective umpolung allylation reaction of amido-tethered allyl carbonates with N-2,2,2-trifluoroethylisatin ketimines has been realized herein. The reaction worked well under mild reaction conditions to give various chiral oxindole derivatives in moderate to excellent yields with high enantioselectivities. Notably, this work represents the first Pd-catalyzed asymmetric umpolung allylation reaction of N-2,2,2-trifluoroethylisatin ketimines.

Comparative study of the reductive decomposition reaction of ethylene carbonate in lithium battery electrolyte: a ReaxFF molecular dynamics study.

Electrolyte decomposition and subsequent solid electrolyte interphase (SEI) are considered to be the primary cause of degradation of lithium batteries. We investigate the multiple factors that can affect the reductive decomposition pathways of ethylene carbonate (EC) and SEI formation using reactive molecular dynamics. Our simulations reveal the effects of lithium concentration, simulation temperature, and the imposition of external electric field on the decomposition reaction and pathways, respectively. The comparative results reveal the increasing lithium concentration has a strong influence on EC decomposition and its pathway at each temperature. Also, the increasing temperature and imposition of an external electric field have been found to non-electrochemically and electrochemically modify the decomposition pathways of EC. This study provides insights into not only the SEI chemistry in Li-ion batteries but also that in lithium metal batteries, which can potentially contribute to the design and optimisation of future novel battery materials and electrolyte solutions.

Low-temperature fabrication of potassium single-atom solid base catalysts with high activity in transesterification

Solid base catalysts are appealing to a variety of reactions due to their benefits of easy separation, negligible corrosion, and environmental friendliness. However, their activity is compromised because high temperature is frequently required for the formation of basic sites and aggregation of basic components is easy to occur under those circumstances. Herein, K single-atom solid base catalysts were fabricated by a low temperature, pyrolysis-free, grafting strategy, resulting in the catalysts with highly dispersed basic sites and high activity in transesterification reaction. Potassium tert-butoxide (KTB) functions as the precursor and mesoporous silica SBA-15 is employed as the support, K atoms are successfully grafted onto SBA-15 (denoted as K1/SBA-15) at 30 °C. Various characterizations confirm that highly dispersed K single atoms exist in the form of K-O-Si. The amount of basic sites of K1/SBA-15 measured by titration is 1.62 mmol·g−1, verifying the basicity of the obtained catalyst. K1/SBA-15 shows excellent activity (49.1 % yield) in the transesterification reaction of ethylene carbonate (EC) and methanol to produce dimethyl carbonate (DMC), which is superior to typical alkali metal-related solid superbases. The catalyst was recovered after reaction and the yield of DMC over the recovered catalyst decreases slightly (43.4 %) due to the partial deformation of pores. Moreover, the K1/SBA-15 exhibits a turnover frequency (TOF) value of 82.5 h−1, obviously higher than various reported solid base catalysts (0.95–36.2 h−1) under semblable reaction conditions.

Construction of diazepine-containing spiroindolines via annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates.

A straightforward synthetic protocol for the efficient construction of diazepine-containing spiroindolines has been developed and proceeds through a by base-promoted annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates. The reaction mechanism of this formal [4 + 3] annulation includes the in situ generated allylic ylide, nucleophilic substitution, Michael additon, and elimination processes. Additionally, the similar reaction with α-halogenated N-tosylhydrazones also afforded N-tosyl-substituted spiro[indoline-3,5'-[1,2]diazepine] in satisfactory yields. This protocol provides a convenient approach for the assembly of diverse highly functionalized spiro[indoline-3,5'-[1,2]diazepines] and also features a broad substrate scope, simple reaction conditions, and high molecular convergence.

Polyhydroxyurethane and Poly(ethylene oxide) Multiblock Copolymer Networks: Crosslinking with Polysilsesquioxane, Reprocessing and Solid Polyelectrolyte Properties.

This contribution reports the synthesis of polyhydroxyurethane (PHU)-poly(ethylene oxide) (PEO) multiblock copolymer networks crosslinked with polysilsesquioxane (PSSQ). First, the linear PHU-PEO multiblock copolymers were synthesized via the step-growth polymerization of bis(6-membered cyclic carbonate) (B6CC) with α,ω-diamino-terminated PEOs with variable molecular weights. Thereafter, the PHU-PEO copolymers were allowed to react with 3-isocyanatopropyltriethoxysilane (IPTS) to afford the derivatives bearing triethoxysilane moieties, the hydrolysis and condensation of which afforded the PHU-PEO networks crosslinked with PSSQ. It was found that the PHU-PEO networks displayed excellent reprocessing properties in the presence of trifluoromethanesulfonate [Zn(OTf)2]. Compared to the PHU networks crosslinked via the reaction of difunctional cyclic carbonate with multifunctional amines, the organic-inorganic PHU networks displayed the decreased reprocessing temperature. The metathesis of silyl ether bonds is responsible for the improved reprocessing behavior. By adding lithium trifluoromethanesulfonate (LiOTf), the PHU-PEO networks were further transformed into the solid polymer electrolytes. It was found that the crystallization of PEO chains in the crosslinked networks was significantly suppressed. The solid polymer electrolytes had the ionic conductivity as high as 7.64 × 10-5 S × cm-1 at 300 K. More importantly, the solid polymer electrolytes were recyclable; the reprocessing did not affect the ionic conductivity.

Effects of kaolinite and halloysite as raw material on solid-state reaction to form kalsilite

This study investigated the effects of the stacking order, morphology, and calcination of kaolinite and halloysite specimens, 1:1 type layered aluminosilicates (Al2Si2O5(OH)4), as raw materials for the solid-state reaction to form kalsilite (KAlSiO4). Thus, this study mainly investigated the solid-state reaction of potassium carbonate (K2CO3) with kaolinite or halloysite specimens at 1000 °C after wet grinding of the reactants. Compared with pristine kaolinite, amorphous KAlSiO4 was generated using disorderly stacked kaolinite by the expansion of its layers as the raw material. Such an amorphous KAlSiO4 was also obtained when halloysite having a tubular morphology with a disputed stacking order was used as the raw material. In addition, the resultant amorphous KAlSiO4 was composed of smaller particles than the KAlSiO4 prepared using kaolinite. When metakaolinite and metahalloysite (i.e., amorphous and dehydroxylated layered aluminosilicates (Al2O3・2SiO2)) were used as raw materials, crystalline kalsilite specimens were obtained. Therefore, the results demonstrated that the crystallinity and particle shape of KAlSiO4 were controlled by the specific types of kaolinite and halloysite as raw materials. Importantly, the stacking order, particle size, morphology, and impurities of kaolinite or halloysite typically vary depending on their geographical origin. Consequently, this study lays the groundwork for the development of cost-effective and environmentally friendly methods for preparing ceramic materials.

A first example of a palladium-catalyzed allylic substitution reaction at a perfluoroalkylene-attached asymmetric carbon center with carbon, nitrogen, and oxygen nucleophiles

Palladium-catalyzed allylic substitution reaction of ethyl tetrafluorocyclopentenyl carbonate or tetrafluorocyclopentenyl methanesulfonate with carbon, nitrogen, and oxygen nucleophiles was systematically investigated. As a result, malonate-derived enolates as a carbon nucleophile, primary and secondary amines as a nitrogen nucleophile, and phenoxide derivatives as an oxygen nucleophile participated all in the reaction very well to furnish the corresponding allylated malonates, allylic amines, and allyl aryl ethers in high yields, respectively. DFT calculations of the reaction mechanism indicate that the direction of nucleophile's attack in the case of carbon nucleophiles, unlike other nucleophiles, is considerably off from the ideal direction, and thus the distance of the newly formed carbon-carbon bond is also considerably longer than the commonly accepted one. It was found then that the activation energies for reactions with carbon nucleophiles were considerably larger than those for reactions with nitrogen or oxygen nucleophiles, and hence the reaction with carbon nucleophiles is less likely proceed.

Regioselective and Diastereoselective Construction of Diverse Dispiro-Indanone-Fluorenone-Oxindole Motifs.

A convenient synthetic protocol for regioselective and diastereoselective construction of complex dispiro-indanone-fluorenone-oxindole motifs was developed by the base-promoted annulation reaction of bindone and MBH carbonates of isatins by adjusting reaction conditions. DABCO promoted the annulation reaction of bindone and MBH carbonates of isatins in DCM at room temperature, affording dispiro[indene-2,4'-fluorene-1',3″-indoline] derivatives in good yields and with high diastereoselectivity. Triethylamine promoted the annulation reaction of two molecular 1,3-indanediones and MBH esters of isatins in ethanol at elevated temperature and selectively gave dispiro[indene-2,4'-fluorene-3',3″-indolines] in moderate yields. However, triethylamine promoted the annulation reaction of excess 1,3-indanediones and MBH esters of isatins in refluxing ethanol, affording dispiro[indene-2,4'-fluorene-3',3″-indolines] with the Z-isomer as the major product and the E-isomer as the minor product.

Crosslinked poly(hydroxyurethane) films from biobased carbonates: Structure-properties relationships and the influence of moisture in the mechanical properties

In this work, crosslinked poly(hydroxyurethane) (PHU) films were prepared by the reaction of biobased cyclic carbonates (BisCC), with different chain lengths, with hyperbranched poly(ethyleneimine) (PEI) under amenable conditions and in the absence of catalysts. Fourier transform infrared (FTIR) spectroscopy revealed that the carbonate groups were completely consumed in the crosslinking reaction and the gel content of the films was about 99 %. It was shown that the thermal and mechanical properties of the PHU films depended on the length of the carbon chain of the BisCC. In the presence of moist environment, the PHU films absorbed moisture (6–8 %) which is ascribed to the presence of hydroxyl groups. This resulted in a deterioration of the mechanical properties, which were not completely recovered after drying. To counteract this effect, a simple procedure was used in which the hydroxyl groups on the surface were modified by stearate groups. Although FTIR and water contact angle measurements demonstrated that the films of PHU became more hydrophobic after modification, the water absorption capacity was similar to that of the unmodified PHU films. This suggests that the modification process may cause some degradation in the bulk of the material that opens spaces for water molecules penetration.In summary, this work has shed light for the first time on the effects of moisture on the mechanical properties of pure PHU films and has shown that surface modifications are not sufficient to prevent moisture absorption.

Electrical energy input efficiency limitations in CO2‐to‐CO electrolysis and attempts for improvement

AbstractElectrochemical CO2 reduction is a potentially up‐coming technology to convert anthropogenic emitted CO2 into chemical feedstock. Due to alkaline operating conditions of CO2‐electrolyis in gas diffusion electrodes, exothermal hydroxide ion neutralization with the excess of supplied CO2 leads to unavoidable electricity‐to‐heat conversion at the cathode, therefore limiting electrical energy input efficiency. The decomposition reaction of carbonates by protons from water oxidation completes the inherent CO2 transport at the anode. In this work, different production routes to CO are thermodynamically examined and experimentally validated. Using formic acid as an intermediate towards CO the electrical energy input efficiency can rise to 71% on a thermodynamical basis. Additionally, the possibility of altering the mechanism of CO2 reduction under acidic conditions is investigated, which would lead to even larger electrical energy input efficiencies. The concept was investigated by pH series measurements (pH = 0–6) at 50 mA/cm2 where Pb derived from Pb3O4 was used as a CO2 reduction catalyst. The reduction to formic acid under acidic bulk electrolyte pH is stable at FEHCOOH = 70% down to pH ≈ 1, while HER is becoming dominant below. Even under such acidic bulk electrolyte conditions no change in reduction mechanism could be forced, which is reflected in invariant cell voltages in the model experiment.

Evolution behavior and kinetic analysis of vacuum-extruded iron-rich dust briquette in blast furnace

The vacuum extrusion iron-rich dust briquette was prepared by vacuum extrusion of iron ore concentrates, blast furnace dust and Portland cement. The evolution behavior and kinetic analysis of briquette in blast furnace was studied by high temperature process interrupted experiment. The phase transformation, metallurgical strength, microstructure and three-dimensional structure of dust briquette during high temperature reduction process were analyzed by X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy and micro computed tomography. It is found that the high temperature reduction process of briquette can be divided into six stages, and the mechanical strength of briquettes under reducing atmosphere decreases with the increase of reduction degree and metallization rate, from 4.58 KN at 100 °C to 0.52 KN at 1100 °C. As the temperature increases, the metal iron and porosity inside briquette gradually increase. The ratio of the volume of metallic iron at 700 °C, 900 °C and 1100 °C was 1.47%, 3.70% and 6.60%, and the porosity is 10.32%, 34.1% and 47.1%, respectively. Furthermore, the non-isothermal kinetic reduction process of briquette was analyzed, and the evolution mechanism was revealed. The reduction process of briquettes is mainly controlled by diffusion, and only in the fourth stage (510 °C–840 °C) is limited by the reduction reaction of magnetite and decomposition reaction of calcium carbonate. This paper provides a theoretical support for the efficient and economical recycling of dust in iron and steel enterprises.

Experimental and Computational Studies on Cobalt(I)‐Catalyzed Regioselective Allylic Alkylation Reactions

AbstractHere, we report the development of cobalt(I)‐catalyzed regioselective allylic alkylation reactions of tertiary allyl carbonates with 1,3‐dicarbonyl compounds. A family of well‐defined tetrahedral cobalt(I) complexes bearing commercially available bidentate bis(phosphine) ligands [(P,P)Co(PPh3)Cl] are synthesized and explored as catalysts in allylic alkylation reactions. The catalyst [(dppp)Co(PPh3)Cl] (dppp=1,3‐Bis(diphenylphosphino)propane) enables the alkylation of a large variety of tertiary allyl carbonates with high yields and excellent regioselectivity for the branched product. Remarkably, this methodology is selective for the activation of tertiary allyl carbonates even in the presence of secondary allyl carbonates. This contrasts with the selectivity observed in cobalt‐catalyzed allylic alkylations enabled by visible light photocatalysis. Mechanistic insights by means of experimental and computational investigations support a Co(I)/Co(III) catalytic cycle.

Experimental and Computational Studies on Cobalt(I)-Catalyzed Regioselective Allylic Alkylation Reactions.

Here, we report the development of cobalt(I)-catalyzed regioselective allylic alkylation reactions of tertiary allyl carbonates with 1,3-dicarbonyl compounds. A family of well-defined tetrahedral cobalt(I) complexes bearing commercially available bidentate bis(phosphine) ligands [(P,P)Co(PPh3 )Cl] are synthesized and explored as catalysts in allylic alkylation reactions. The catalyst [(dppp)Co(PPh3 )Cl] (dppp=1,3-Bis(diphenylphosphino)propane) enables the alkylation of a large variety of tertiary allyl carbonates with high yields and excellent regioselectivity for the branched product. Remarkably, this methodology is selective for the activation of tertiary allyl carbonates even in the presence of secondary allyl carbonates. This contrasts with the selectivity observed in cobalt-catalyzed allylic alkylations enabled by visible light photocatalysis. Mechanistic insights by means of experimental and computational investigations support a Co(I)/Co(III) catalytic cycle.

Response of Foraminifera to Anthropogenic Nicotine Pollution of Cigarette Butts: An Experimental Approach

The most often dispersed environmental pollutants that are released both directly and indirectly into the environment that may eventually reach aquatic ecosystems and contaminate aquatic biomes are cigarette butts (CBs). Toxicants such as nicotine, dangerous metals, total particulate matter, and recognized carcinogens can be introduced and transported via CBs into aquatic ecosystems. The examination of the effects of synthetic nicotine on three different species of cultured benthic foraminifera was the focus of this study. Three foraminiferal species from three distinct biomineralization pathways were specifically examined for viability and cellular ultrastructure, including the calcareous perforate Rosalina globularis, the calcareous imperforate Quinqueloculina spp., and the agglutinated Textularia agglutinans. The survival rate, cellular stress, and decalcification were used to assess the toxicological effects of synthetic nicotine. We were able to analyze the reaction of major macromolecules and calcium carbonate to this pollutant using FTIR (Fourier Transform Infrared) spectroscopy. High Performance Liquid Chromatography (HPLC) study was performed to increase our understanding of nicotine bioavailability in the medium culture. Different acute experiments were performed at different dates, and all indicated that synthetic nicotine is acutely hazardous to all three cultured foraminiferal taxa at lethal and sublethal concentrations. Each species responded differently depending on the type of shell biomineralization. Synthetic nicotine enhances shell decalcification and affects the composition of cytoplasmic macromolecules such as lipids and proteins, according to the FTIR spectroscopy investigations. The lipid content rose at lethal concentrations, possibly due to the creation of vesicles. The proteins signal evidences general cellular dyshomeostasis. The integration among the acute toxicity assay, synchrotron, and chemical HPLC analyses provided a valuable approach for the assessment of nicotine as a biomarker of exposure to the toxicants associated with smoking and the impact of this emerging and hazardous material on calcifying marine species.